I finally bought a rack for the jeep -- a Kargo Master Congo Cage, bought it from 4wheelparts.com and they had free shipping to a local store.  Nice deal on a rack with a 500lb dynamic (!) load rating.  I also picked up the "utility crossbar" kit for the rack, it adds two 66" x 2" crossbars, very sturdy.

The rack itself goes together pretty easily. The brackets bolt onto the top of the windshield hinges and where the rear bumper attaches to the frame. Both appear to be very sturdy attachment points. You have to use a lot of silicon sealant in the process, and it's very messy to be sure to pick up some surgical gloves. The instructions are not bad, I basically put all the brackets on and then assembled the rack from back to front. It took me about four hours and I feel like I took my time.

I've got more pictures at my smugmug site, here's a few:









The rack attaches to the windshield hinges in front:



and to the rear bumper where it meets the frame. It's a little hard to see, it's the bracket in the center of this image:



The bracket lets the rack attach just above the rear bumper. It looks like it rests on the bumper, but it doesn't.





After crawling around on a trail, I noticed that the rack has a tendency to rock front to back if you're juddering along in low range. It seems like this is OK, hopefully it won't stress the welds too much... I decided to put some rubber stoppers on the front support pillars, this should keep it from rocking too far and from hitting the windshield frame.

This is a rubber stopper I bought at Lowes, size #9-1/2. I drilled a hole through it for the zip tie and cut out a bit of a channel in it so that it would sit on the cage frame better. I applied a healthy coat of RTV sealant to help keep it in place and cinched down the zip tie. If the cage rocks too far back it should just push the stopper against the top of the windshield frame.